This invention relates to a method for controlling a transfer case and more particularly, to a method for controlling a transfer case within a four wheel drive vehicle which provides an improved response by monitoring and reacting to the position or angle of the vehicle""s steering wheel.
Four-wheel drive vehicles typically include a transfer case which selectively transfers torque and power from the vehicle""s input shaft to a front and a rear driveshaft, thereby selectively rotating the front and rear driveshafts. The transfer case includes a conventional electromagnetic clutch assembly which typically and selectively transfers torque from a primary driveshaft (e.g., the rear driveshaft) to a secondary driveshaft (e.g., the front driveshaft), thereby reducing the torque provided to the primary driveshaft and increasing the torque provided to the secondary driveshaft. The clutch assembly is typically and communicatively coupled to a controller and/or control system which determines the amount of torque that is to be provided to the front and rear driveshafts (e.g., primary and secondary driveshafts), based upon vehicle sensory data, and which generates a control or command signal to the clutch assembly, thereby controlling the amount of torque which is provided to front and rear driveshafts. Particularly, in order to provide torque and traction to the front and rear wheels of the vehicle and to avoid relative slip between the front and rear wheels, the transfer case controller and/or control system typically monitor the speed of both the front and rear driveshafts and the position of the vehicle""s throttle (i.e., xe2x80x9cthrottle positionxe2x80x9d).
While these types of prior systems provide sufficient traction and control to the front and rear wheels of a vehicle in many situations, they suffer from some drawbacks. One drawback associated with these prior systems is that, while they typically monitor and react to the throttle position and the respective speeds of the front and rear wheels, they do not monitor the angle and/or position of the steering wheel of the vehicle. Hence, these systems do not adequately account for situations in which the front and rear wheel speeds naturally differ, such as when the vehicle is engaged in a turn. These prior systems must allow for an undesirable amount of slip to compensate for situations in which the vehicle is in a turn. As a result, these prior systems often allow slippage to occur between the front and rear wheels of the vehicle, or cause and/or suffer from undesirable noise and vibration harshness (xe2x80x9cNVHxe2x80x9d), which is perceived by the operator and/or passengers of the vehicle.
There is therefore a need for a method and an apparatus for controlling a transfer case within a four-wheel drive vehicle which provides an improved response by monitoring and considering the position or angle of the vehicle""s steering wheel.
It is a first object of the invention to provide a method and an apparatus for controlling a transfer case within a four-wheel drive vehicle which overcomes at least some of the previously delineated drawbacks of the prior systems, devices, and/or methods.
It is a second object of the invention to provide a method and an apparatus for controlling a transfer case within a four-wheel drive vehicle which monitors and desirably reacts to the position or angle of the vehicle""s steering wheel.
According to a first aspect of the present invention, a system for controlling a transfer case is provided. The transfer case is operatively disposed within a four-wheel drive vehicle of the type having a steering wheel and a primary and a secondary driveshaft, and is effective to selectively transfer torque between the primary and secondary driveshafts. The system includes a sensor which senses an angle in which the steering wheel is positioned and which generates at least one signal representing the sensed angle; and a controller which is communicatively coupled to the transfer case and to the sensor, which receives the at least one signal and which utilizes the at least one signal to selectively generate an output signal which is based upon the sensed angle and which is effective to selectively control the torque which is transferred to the primary and secondary driveshafts.
According to a second aspect of the present invention, a method is provided for controlling a transfer case which is operatively disposed within a four wheel drive vehicle. The vehicle is of the type having a selectively positionable steering wheel, a front driveshaft and a rear driveshaft. The transfer case is adapted to selectively provide torque to the front and rear driveshafts. The method comprises the steps of: determining an angular position of the steering wheel; using the angular position to calculate a minimum duty cycle value; and selectively providing the minimum duty cycle value to the transfer case, effective to alter the torque provided to the front and rear driveshafts.